To provide a thin steel plate with extremely less surface defect originating in cracks caused in the hot rolling, even in the straight forward rolling process and its manufacturing method.
A steel material containing C: 0.2% or less, Si: 1% or less, Mn: 0.4 to 2.0%, P: 0.8% or less, O: 0.005% or less, S: 0.03% or less, N: 0.01% or less, Sn: 0.004% or less (all in mass percent) is east in a continuous casting machine, and then the steel material is held for more than five minutes in the surface temperature of the slab: 950 to 1150 degrees C and by avoiding the temperature range wherein the surface temperature of the cast slab reaches more than 750 degree C and less than 850 degree C, a bending deformation is performed so that the distortion speed on the surface shows 1×10-4 to 1×10-1 and after a draft in the width direction in the roughing roll, plural drafts in the plate thickness direction are performed at the distortion speed of 1/second or more.
TSUCHIYA YOSHIRO
KIKUCHI HIROYASU
| JPS6240960A | 1987-02-21 | |||
| JPH0776375B2 | 1995-08-16 | |||
| JPS60262915A | 1985-12-26 |